Today, text, audio, and video content (“content”) can be transmitted using a number of technologies. For example, a server on the Internet can transmit a video clip to a plurality of users. Such a process is typically referred to as “streaming.” A number of challenges exist, however, for streaming content on the Internet. One challenge is content protection. The challenge of content protection relates to preventing illegal copying and distribution of premium content. Another challenge is bandwidth economics. The challenge of bandwidth economics relates to transmitting content within a limited bandwidth.
One method for content protection is watermarking. Watermarking is a process of inserting unique information (“watermark”) into content in a non-removable manner. That is, an attempt to remove the watermark may cause loss of all or part of the original content. A watermark is a form of rubber-stamping, e.g., a frame of a motion picture, with a unique signature. Typically, for a server on the Internet to perform watermarking, the server must send content with a different watermark for each user. Thus, a disadvantage of the watermarking process alone is that each item of content must be uniquely watermarked for each user or entity to whom the content is to be distributed. If the number of users to receive the content is large, watermarking can be bandwidth intensive and very complex for the server.
Another method for content protection is content encryption or scrambling. For example, in order to prevent unauthorized copying of content, the content can be encrypted with one or more keys and decrypted by users with correct keys to access the content. Generally, the content is both compressed and encrypted. A disadvantage of encrypting content alone is that after decrypting and descrambling the content unauthorized copies of the content can still be made. To locate the source of such unauthorized copying, a fingerprint or watermark can be added to content to indicate the content is copyright protected. A problem with adding a watermark to encrypted content is that it must be first decrypted before the watermark can be added. Consequently, if the content is encrypted, access to the content is not available. Moreover, adding watermarks and decrypting content requires extensive processing capacity.
One method to address bandwidth constraints is multicasting. Multicasting is the process of a single server sending content to multiple users at the same time. For example, a server on the Internet can send a video clip once (“multicast”) to many users. Thus, a single server can send content to many users without either the server or the network becoming too congested. A disadvantage of multicasting alone is that it is difficult to protect the content being multicasted. For instance, multicasting is incompatible with existing watermarking technology because multicasting relies on all users receiving exactly the same data. Watermarking, however, relies on all users receiving uniquely “stamped” data. As such, a number of problems exist with distributing content such as text, audio, and video data on the Internet that relate to providing content within bandwidth constraints and ensuring content is protected or identified.